Glacis
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[edit] Glacis (military or engineering)
A glacis (/ˈgleɪ.sɪs/ or /ˈglæ.si/) in military engineering is an artificial slope of earth in the front of works such as fortifications, so constructed as to keep any potential assailant under the fire of the defenders to the last possible moment. On the natural ground level, troops attacking any high work have a degree of shelter from its fire when close up to it; engineers therefore raise such ground to form a glacis, which defenders can sweep with fire from the parapet. The glacis was originally designed to protect stone fortifications, as vertical walls could easily be smashed down by artillery fire. The glacis deflected incoming cannonballs by providing a springy, sloping surface which the cannonballs bounced off, landing behind the fragile stone fortifications.
More generally, the term glacis can denote any slope, natural or artificial, which fulfils the above requirements.
The etymology of this French word suggests a slope made dangerous with ice, hence the relationship with glacier.
The term glacis plate describes the upper front hull armor of a tank or other armored fighting vehicle, as well as the armored plates attached to certain artillery and machine gun pieces.
[edit] Glacis (Geology)
An erosional or depositional pediment, with little slope. Erosional glacis occur mostly in arid regions, and result from intense meteorization and surface transport via laminar, episodic water flow.
